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View Full Version : 535i - M30B35 surging


Trevor M
07-13-2009, 12:01 AM
Cruising along today and my car decides to do a dump. Started surging & couldn't maintain speed. Idles fine but when I accelerate it starts cutting out again. At first I thought I filled up with bad gas but I'm guessing the TPS went kaput because when I get the engine over 1500 RPM it cuts out. The harder I press the pedal the more violent the surging gets. With a top speed of 60Km/hr I limped home about 30 Km on back roads because people were getting pissed at me :D. One guy in the Dodge Neon must have felt good about himself beating an Alpina :stickoutt

Aside from the TPS, is there anything else that would cause this?

Tomorrow I'll swap throttle switches with my 635CSi to see if that's the culprit.
m60b30530i
07-13-2009, 09:28 AM
check the afm, or maf , temperature sensor and coolant sensor for the fuel injection system.
Binjammin
07-13-2009, 09:43 AM
Can you take a video of the engine while it's surging?
Trevor M
07-13-2009, 02:52 PM
Went out this morning and swapped throttle switches from my other car. Took it for a spin and everything appeared normal ...until it hits 4k then it does the shutoff/surging again. I swapped the old switch back in....same thing. Only thing, at 4k and WOT it's more violent than 1500RPM. At WOT I have full power & pulls hard until it hits that magic number (1500 yesterday, 4000 today). I think the difference is because it's cooler now and it was a lot hotter last night.
Thinking maybe it was a failing fuel pump I connected a gauge. I have...
35PSI idle
43PSI no vacuum
30PSI full vacuum

I'm going to take it for a spin with the fuel pressure gauge connected. Maybe I have a flow problem but I don't think so because of how hard it pulls at WOT below the 4k threshold.

Still have to look at the AFM...hope it's not the DME! :eek:

I replaced the CPS a few weeks back because the wires were cracking with a brand new aftermarket sensor. Possible it failed? It would quit altogether instead of doing this speed limiter thing, no?


Can you take a video of the engine while it's surging?

Don't have a camera that does vids. I'll see if I can borrow one if this persists